Failing with "failed with weakmap value was not a string" error

We're trying to upgrade our project to Ruby 3.3.6 from Ruby 3.2, and as part of that change we suddenly started getting warnings that we weren't getting before.

We're using prometheus-client-mmap through https://github.com/yabeda-rb/yabeda-prometheus-mmap and we're now seeing the following every time a measurement is taken:

WARN -- : writing value to /var/folders/bp/z2fzv5z93xsddj25znk3_0w80000gn/T/prometheus-mmap20241204-52507-aque7r/histogram_52507-0.db failed with weakmap value was not a string
DEBUG -- : /.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_dict.rb:46:in `upsert_entry'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_dict.rb:46:in `write_value'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_value.rb:139:in `write_value'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_value.rb:34:in `block in increment'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_value.rb:30:in `synchronize'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/mmaped_value.rb:30:in `increment'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/histogram.rb:31:in `block in observe'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/histogram.rb:30:in `each_key'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/histogram.rb:30:in `observe'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/histogram.rb:65:in `block in observe'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/metric.rb:76:in `synchronize'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/metric.rb:76:in `synchronize'
/.../prometheus-client-mmap-1.0.1/lib/prometheus/client/histogram.rb:65:in `observe'
/.../yabeda-prometheus-mmap-0.4.0/lib/yabeda/prometheus/mmap/adapter.rb:60:in `perform_histogram_measure!'

The backtrace is for version 1.0.1 which is the version we were on in Ruby 3.2, but I'm also seeing this on the latest version (1.1.1). Seems like some sort of Rust issue AFAICT. We're also seeing this for "read_value" calls.

Any insights? Any additional information I could provide? I'm currently running Ruby 3.3.6 on a Macbook with an M3 processor.